Reading Astronomy News

Reading Astronomy News: ESO Telescope Reveals What Could be the Smallest Dwarf Planet yet in the Solar System

Eso1918a
ESO/P. Vernazza et al./MISTRAL algorithm (ONERA/CNRS)

By Stacy Palen

According to this article by the ESO, Hygiea has been imaged by ESO’s VLT. It is round, which makes it a dwarf planet rather than an asteroid. Smaller than Ceres, it is now the smallest known dwarf planet in the Solar System.

 

1) Study the image of Hygiea at the top of the article. The image of this tiny object is a little bit fuzzy, despite the powerful telescope used to obtain it. Nonetheless, some features are visible. Describe the surface of Hygiea.

Hygiea appears to have some craters, with variations in height as well as variations in brightness.

 

2) Until this image was taken, astronomers were not sure whether to categorize Hygiea as an asteroid or a dwarf planet. Which criterion for dwarf planet status could be determined from this image?

Hygiea has enough gravity to pull itself into a round shape.

 

3) The article compares Hygiea’s size (430 km) to that of both Pluto (2400 km) and Ceres (950 km). Roughly how many times larger are these other dwarf planets than Hygiea?

Ceres is a bit more than twice as large, and Pluto is about six times larger.

 

4) Describe the origin of this dwarf planet, in your own words.

A much larger planetesimal collided with a smaller one about 2 billion years ago. The explosion created 7,000 asteroids, at least one of which had enough gravity to form a dwarf planet.


Reading Astronomy News: Giant Radio Telescope in China Just Detected Repeating Signals from Across Space

A74YFG
Stocktrek Images, Inc./Alamy Stock Photo

By Stacy Palen

Fast radio bursts have been known since 2007. Recently, China’s FAST telescope has detected a repeat of one first discovered at Areceibo in 2012. This article poses several explanations for fast radio bursts.

Questions:

1) Study the picture of the 500-m telescope at the top of the article. Is this a “steerable telescope?"

Answer: No, this telescope is far too large to be steerable.

 

2) Describe how a telescope that is not steerable “sees” the sky differently than a steerable telescope.

Answer: A telescope like this can see only the portion of the sky that passes through its zenith. Because it is not steerable, it cannot track an object, so the observing time is set by the amount of time it takes for the object to pass through the field of view.

 

3) The signal was emitted from a source 3 billion light-years away. How long has the signal been travelling to reach us?

Answer: The signal has been traveling for three billion years.

 

4) What was happening on Earth when this signal left the source?

Answer: The earliest forms of photosynthesis date from around this time.

 

5) Why is a repeating FRB so interesting to astronomers?

Answer: If the FRB repeats, that rules out a whole class of causes. The object has clearly not blown up, so this is not connected to supernovae or black hole mergers.

 

6) Choose one of the proposed explanations for FRBs and explain in more detail how an FRB could be caused in that way.

Answer: Answers will vary.


Reading Astronomy News: Our Galaxy’s Black Hole Suddenly Lit Up and Nobody Knows Why

PIA18919
Image credit: NASA/JPL-Caltech

By Stacy Palen

Sgr A* is flaring to twice peak historical levels, possibly because of gravitational disturbance from S0-2. This particular article from Vice News provides a good opportunity to help students see when they are being “click-baited,” since “Nobody Knows Why” is a bit of a tease. There are actually several explanations for why this might happen, as the article later explains.

 

1) “Flux” may be a new vocabulary word, particularly in this context. Look it up and summarize the definition that is relevant to this article in your own words.

Flux is the light emitted per second per square meter.

 

2) The article states that we have been monitoring Sgr-A* for about 20 years. What technological improvements made a monitoring campaign like this one possible?

We needed to be able to observe in the infrared at high enough resolution to avoid confusion of sources in this tightly packed region of the Galaxy.

 

3) What possible causes for the flare are given in the article?

A close pass of SO-2 may have disturbed the gas near the black hole. We may be seeing a delayed reaction from a dust cloud that passed by and was torn apart.

 

4) Notice the article’s title: “…and Nobody Knows Why”. Do you think that this is an accurate characterization of what astronomers know about this flare? Why do you think the article’s title was written in this way?

Answers will vary for the first question; the second answer should include something about baiting people to click on the story.


Reading Astronomy News: Lost Cities and Climate Change

By Stacy Palen

3391748349_d7f071c9bd_o
Remnants of the lost city of Cahokia. Credit: Steve Moses/Flickr (CC BY 2.0)

 

In this article from Scientific American, a climate scientist talks about why she is not reassured by the idea that “the climate has changed before.” This is an opinion piece, but it is worth a read if you have students who raise this argument.

 

1) The author points out that climate has changed many times in the past. Does that imply that Earth’s climate is sensitive to small changes or insensitive to small changes?

It implies that Earth’s climate is very sensitive to small changes.

 

2) This scientist is making the case that historical climate change has had dramatic and long-lasting effects on human communities. Do they provide evidence to support this argument?

Yes. The author mentions many examples, from both prehistoric and historic times.

 

3) The author also makes the case that many factors contributed to these effects. Identify an example of a pre-existing condition that was made worse by natural climate change.

Answers vary, but the overextended Roman empire or inequality in France might be mentioned.

 

4) Do you see any evidence for a similar pre-existing condition in the country today? Explain.

Answers will obviously vary depending on where you live. This is a small test of how well-informed students are about what’s happening in the larger society.

 

5) Describe how climate change might impact the condition you noted in (4).

Answers will vary, but should be consistent with their answer to 4. So, for example, if they mention immigration, they might include here a mention of how drought drives migratory patterns.

 

6) In your own words, explain the argument this scientist proposes that historical climate change should be seen as concerning rather than reassuring.

Answers will vary based on the students’ comprehension of the post.

 


Reading Astronomy News: Japan (Very Carefully) Drops Plastic Explosives Onto An Asteroid

Capture1
By Stacy Palen

Summary: Hayabusa2 has been investigating the asteroid Ryugu. This is a sample-return mission, which has implications for Solar System formation and may cast light on the origins of life on Earth.

Article: Japan (Very Carefully) Drops Elastic Explosives Onto an Asteroid

1. Consider what you know about the origin of the Solar System. What are astronomers hoping to learn from Hayabusa2’s mission to Ryugu?

Answer: They are hoping to learn about the composition of matter in the Solar System when it formed. This could confirm or refute our ideas about Solar System formation and the formation of the asteroid belt. The precursor molecules for life are also present on the asteroid, which may give us clues about the origins of life on Earth.

2. The article states that Hayabusa2 “physically touched down” on Ryugu in February 2019, and took a sample of dust kicked up. Go online and read more about it. Describe this event in more detail. Do you consider “physically touched down” to be an accurate characterization of what happened?

Answer: The spacecraft approached the surface and shot a small projectile into the asteroid. A sampler horn collected the kicked up dust and the spacecraft moved on. This is not quite what’s implied by the summary sentence in the news article.

3. Ryugu is less than a mile across, in an orbit between Earth and Mars. Using an average orbital radius between those two planets (1.25 AU), find the orbital period of Ryugu. Convert this orbital period to seconds.

Answer: This is a review of Kepler’s third law. The period is 1.16 years, which equals 3.7 X 107 seconds.

4. The circumference of Ryugu’s orbit is 1.2 X 1012 Divide this distance traveled by the period to find the speed of the asteroid in its orbit. This is the speed that Hyabusu2 must be traveling in order to rendezvous with the asteroid.

Answer: This is a reminder of the definition of the properties of an orbit (what is the circumference, and what is the period). The speed is 32,000 m/s.

5. When was the spacecraft launched, and when is the sample return mission expected to arrive back here on Earth?

Answer: The spacecraft launched in December 2014, and will return a capsule to Earth in December 2020.

 

Image Contributor: Mark Garlick/Science Photo Library, 1 March 2013


Reading Astronomy News: Galactic Superbubbles

Capture
By Stacy Palen

It’s that time of the semester when we are talking about galaxies, galactic structure, and supermassive black holes. Fortunately, Chandra has our back and has released a new image of a superbubble in NGC3079. The picture is sufficiently spectacular that I want to let you know about it right now!

Article: NGC: Galactic Bubbles Play Cosmic Pinball with Energetic Particles

1. Along the bottom of the composite image on the website, there are tabs that allow you to switch back and forth between the composite image, the X-ray image and the optical image.  Compare the X-ray image and the optical image. 

Answer: The X-ray image contains mostly just point sources, as well as two larger fuzzy patches. One of these fuzzy patches is shaped like a ring. The optical image, however, shows the entire galaxy, including dark lanes of dust and gas and bright light from stars and emission nebulae.

2. How big are the superbubbles, compared to the diameter of the disk of the Milky Way Galaxy?

Answer: The superbubbles have diameters of a few thousand light years. The disk of the Milky Way has a diameter of a few hundred thousand light years. So, these bubbles are about 1/100 (0.01 or 1%) the size of the Milky Way’s disk.

3. What is a cosmic ray? 

Answer: A high energy positively charged particle traveling through space. Note: they will have to click through to find this answer, if they don’t already know it! Let’s encourage that behavior!

4. Humans also accelerate particles, in particle accelerators, funny enough. How much more energy do the particles in these bubbles have than those accelerated by humans?

Answer: These particles have 100 times more energy than those in particle accelerators.

5. Run your mouse over the composite image to see it with labels on it. Why do astronomers think these superbubbles are associated with a supermassive black hole?

Answer: Because they are located together in space. 

 

 Photo credit:

 X-ray: NASA/CXC/University of Michigan/J-T Li et al.; Optical: NASA/STScI

 


Reading Astronomy News: Chasing Down the Mystery

AT2018Cow
Credit: Sloan Digital Sky Survey, www.sdss.org

 

Once in a while something new happens. In the case of an article published in The Atlantic, astronomers observed an object that had properties like those of a supernova explosion, but much too fast. That led to some detective work across the electromagnetic spectrum to try to figure out what was happening!

 

1. What event triggered astronomers to pay attention to this particular location in space?

Answer: A bright spot appeared where none had been before.

 

2. How did astronomers communicate with each other that something interesting was happening?

Answer: They used The Astronomer’s Telegram, a global astronomy alert system.

 

3. Where did the event happen?

Answer: This event occurred in a nearby galaxy. It was detected at a telescope in Hawaii. (Note: I would use answers to this question to find out if students have sorted out what an “event” is, and the difference between an “event” and the detection of it.)

 

4. What about this event made it clear that this was not a “normal” supernova?

Answer: It was too bright, and also faded away too quickly. This is weird because brighter supernovae should fade away more slowly, not more quickly.

 

5. What is the current working hypothesis about what happened in the event?

Answer: Astronomers think this may have been the formation of a black hole or a neutron star.

 

6. How will astronomers test this hypothesis?

Answer: This event is over, so astronomers will have to wait for another one to occur to test their ideas against observations of that future event.


Reading Astronomy News: Earth’s Magnetic Field On The Move

Earth's Magnetic field
Image Credit: Emmanuel Masongsong/UCLA EPSS/NASA

By Stacy Palen

In January, geologists updated the model of Earth’s magnetic field, a year ahead of schedule.

 

1. Study the map titled “Magnetic Motion.” How much time separates each pair of red dots between 1900 and 2010?

Answer: The dots indicate 10-year time intervals until 2010. There is an extra dot placed for 2015.

 

2. In general, how does the movement of the magnetic pole since 1990 compare to the movement of the pole prior to that time?

Answer: Because the red dots are much farther apart after 1990, we can conclude that the pole is moving a lot faster in the last few decades than it did prior to that.

 

3. Why do we care about what happens to the magnetic pole of Earth?

Answer: The position of the magnetic pole underlies all navigation. If we don’t know where the pole is, we don’t know where we are.

 

4. Why did geologists decide to update the model a year earlier than expected?

Answer: Because the position of the pole was changing so fast that navigation was becoming inaccurate.

 

5. What is the working hypothesis for why the position of the magnetic pole is changing so rapidly right now?

Answer: A jet of liquid iron is weakening the magnetic field in Canada. This means that a second patch of magnetic field in Siberia is relatively stronger, so the pole is moving in that direction.

 

6. How does this news article relate to what you have learned about Earth’s magnetic field?

Answer: We have learned that Earth’s magnetic field changes over time, and that the history of those changes are recorded in rocks. We have also learned that the magnetic field affects the aurorae in Earth’s atmosphere. As the magnetic field changes, this should affect the aurorae as well.


Reading Astronomy News: The Lyrids are Coming!

Meteor Shower

Image Credit: NASA/Bill Ingalls

By Stacy Palen

Don’t forget to remind your students to watch for the Lyrid Meteor Shower this month. The peak occurs around April 21-22.

This meteor shower comes as Earth passes through the debris left behind by Comet Thatcher. Particles lost from the comet continue to drift in the Solar System, gradually changing their position.

As Earth moves through space, it passes near the trajectory of the comet and runs into collections of these particles. This will happen repeatedly at particular times of the year as Earth returns to the same point in its orbit. The particles burn up, creating meteors as they fall through the atmosphere.

Comet Thatcher has a 415 year orbit, so it is a long-period comet. It will not be back in the inner Solar System until 2276.

To watch a meteor shower, go to a clear dark site where the horizon is not obstructed. Spend about half an hour in the dark, without your cell phone or other bright light in view. This will allow your eyes to adapt to the dark. Then just watch for meteors! They are best seen with the naked eye.

If you are careful and methodical, your observations can contribute to the study of meteors and meteor streams! To learn more, visit the Astronomical League’s Meteor Observing Program website.


Reading Astronomy News: Updated Graphic of LIGO/Virgo Compact Binaries

By Stacy Palen

LIGO has been busy, and a newly released graphic summarizes many of the exciting discoveries the detector has made in concert with Virgo, its European counterpart.

Summary: Since 2015, the LIGO/Virgo collaboration has detected gravitational waves—ripples in spacetime caused by rapidly accelerating massive objects—from 10 stellar mass binary black hole mergers and one binary neutron star merger. Black holes and neutron stars are both forms of stellar remnants—the final stage of stellar evolution that a star enters when it has burned through its entire fuel supply. This graphic provides a great jumping off point for discussions about masses in the stellar graveyard.

Questions:

1. Consider the final masses of the black hole mergers (larger blue circles). What is the smallest merged mass?

Answer: About 19 solar masses.

 

2. Consider the masses of black holes that have been detected in X-rays (EM Black Holes, in purple). What is the largest black hole mass that has been detected this way?

Answer: About 23 solar masses.

 

3. Estimate the average mass of the black holes that have been detected in X-rays.

Answer: About 10 solar masses.

 

4. Estimate the average mass of the black holes that have been detected in gravitational waves.

Answer: This average looks to be about 25 solar masses.

 

5. Astronomers make the claim that they are detecting a “new population of black holes” with gravitational waves---—that is, that the type of black holes they are detecting now are different than the ones they were detecting before. Based on your answers to questions one through four, explain why they would say this.

Answer: Even though the two groups of black holes overlap in mass, gravitational waves are detecting more massive black holes, on average, than were detected with X-rays in the past.

 

6. Compare the number of EM black holes to the number of black holes (before merging) discovered with LIGO/Virgo. How much has LIGO/Virgo contributed to the total sample of known black holes?

Answer: LIGO/Virgo has nearly doubled the number of black holes that have been observed.

 

7. Is it reasonable, then, to compare the two populations (the pre-merger black holes from the LIGO/Virgo data and the X-ray black holes)?

Answer: Yes, statistically speaking, we know of about the same number of objects in each case.

 

8. Consider the masses of Neutron stars (yellow). What is the largest neutron star mass that has been detected with light (EM)?

Answer: About 2.1 solar masses.

 

9. Consider the masses of Neutron stars (yellow). What is the average neutron star mass that has been detected with light (EM)?

Answer: About 1.5 solar masses

 

10. Theorists predict that we would not expect to observe neutron stars with masses above about 2.14 solar masses. Are these observations consistent with that prediction? What do you think astronomers are wondering about the post-merger object resulting from the merger of two neutron stars?

Answer: The neutron stars observed with light are consistent, but the outcome of the neutron star merger is a little bit too massive. As of this writing, astronomers are still trying to figure out the form of that post-merger object. It could be a black hole, a neutron star collapsing to form a black hole, or a stable neutron star. More data are needed!